In general, a heat exchanging apparatus of a boiler is to absorb combustion heat generated from a burner, and includes heat exchanging pipes through which water flows and heat transferring fins for absorbing the combustion heat, so as to heat water using the combustion heat in order to make hot water.
FIG. 1 is a schematic view showing the structure of a conventional gas powered boiler.
In a heat exchanging apparatus 1, heat energy generated by a burner 20 is transferred to a heat exchanger 10 so as to heat water in the heat exchanger 10. The heated water is forcibly supplied to locations which require heating by a circulation pump (not shown), so as to transfer heat. At this time, a blower 30 is installed at a lower portion of the burner 20 in order to effectively transfer heat energy to the heat exchanger 10. Meanwhile, exhaust gas is discharged through a smoke tube 40.
The hot water circulated by the circulation pump transfers its heat to the locations which require heating, and then returns to the relatively cold water so as to be introduced through inlet into the heat exchanger 1. This process is repeated, the calefactory water is continuously circulated.
In the boiler having the above mentioned structure, when much time passes in the state that the operation of the boiler stops, all of pipes in the boiler, the heat exchanger, pipes connected from the boiler to rooms respectively, and pipes arranged in the rooms are fully filled with cold water of which temperature has dropped. Further, the temperature of water in the pipes for heating becomes lowered to level identical with temperature of air around the boiler.
When the boiler operates in a state that the temperature of the water in the heating pipe has been lowered, there occurs temperature difference between the cool water in the heating pipe and heated air due to the combustion of the burner.
Such a temperature difference seriously occurs in winter when a temperature of water in heating pipes is very low. Moisture, which is contained in the atmosphere, is condensed on a peripheral surface of pipes of the heat exchanger 10, so as to be condensate water.
Meanwhile, the calefactory water, which returns after transferring heat to locations which require heating, has a lowered temperature. Therefore, when the calefactory water of which the temperature is low passes through the pipes in the heat exchanger, the temperature difference between cold water in the pipe and the atmosphere heated to high temperature causes moisture contained in the atmosphere to condense on the peripheral surface of the pipes.
The water condensed on the peripheral surface of the pipe naturally evaporates. However, in a hot water supplying apparatus, combustion gas is generated and reacts with the condensed water so as to create acidic condensation water while fuel oil or gas is combusted in a combustion chamber.
Such acidic condensate water accelerates the corrosion of various parts, made of metal material, of the heat exchanger, thereby curtailing the lifetime of the heat exchanger.